ZHAI Yanan, CHEN Qibo, LI Jianqiang, YANG Jianguang, QIAN Jing
Effects of prescribed burning on slope runoff and sediment yield in Pinus Yunnanensis forest
[Background] Prescribed burning is a management practice that aims to reduce the fire risk. The main objective of this study is to explore the impact of prescribed burning on slope runoff and sediment yield in Pinus yunnanensis forest. [Methods] The runoff and sediment yield were estimated by runoff plots method from May to October in 2020, and the rainfall were obtained self-recording rain gauge (Onset HOBO RG3-M). Base on the observation data from 2 plots established respectively in the burned and unburned forest land in Zhaobi Mountain of Yunnan province, the runoff and sediment yield between burned and unburned forest land were compared via Excel 2010, SPSS26 and Person correlation analysis. And then, the numerical relationship model between rainfall and runoff, sediment yield were built using 1 stopt software. [Results]1) In 2020, the total rainfall in the study area reached 903.2 mm, which was 33.45 mm less than the mean annual rainfall and with approximately 73.64% of rainfall occurring in the rainy season from May to October. 2) After the implementation of the prescribed burning, the runoff and sediment yield significantly increased, the runoff and sediment yield in the prescribed burning plot was 3.01 and 20.92 times as much as that in unburned plot, respectively. 3) Based on the correlation analysis, it was found that runoff yield and sediment yield were significantly correlated with rainfall. 4) The generalized model illustrated that the runoff linear related with the rainfall and rainfall intensity in unburned plots, and the runoff was power function to rainfall and rainfall intensity in burned plots. However, the sediment yields in burned and unburned plots were power function to rainfall, rainfall intensity and runoff in burned and unburned forest land. [Conclusions] Prescribed burning significantly reduced the ability in adjusting on forest hydrological function and increased the amount of soil erosion in P. yunnanensis forest land. However, the erosion modulus in the prescribed burning forest land was much lower than the local allowable soil loss value of 500 t/(km2·a). This study will provide baseline information for accessing the ecological effects by prescribed burning in forests.
CUI Liqiang, YUAN Limin, ZHAO Mingyan, CONG Wencheng
Protection effect of jute fiber slope protection on water erosion
[Background] Huolinhe Opencast Coal Industry Co., Ltd., piled up the wastes from coal mining in the open air, forming many giant artificial loose piles. The hills in the site are relatively steep and without any protective measures. Due to water erosion, a large number of eroded trenches are formed on the surface of the slope, and the vegetation growth is poor, which is very prone to landslide hazards. The soil erosion problem of the dump in this area has seriously affected the normal production of the mine, and caused the mine to suffer huge economic losses. [Methods] In this study, jute fiber slope protection was used to control the water erosion of the dump slope in the coal mine area, and water erosion protection effects of different types and specifications of jute fiber slope protection on different parts of slope were compared. Wooden piles were set up in the upper, middle and lower parts of the test area respectively. The height of wooden piles was measured 3 months, 15 months and 27 months after the slope protection was set up. The degree of water erosion on the slope was judged according to the numerical value. [Results] 1) The first year, jute fiber slope protection significantly inhibited the soil erosion depth on the slope surface and the slope gullies. The soil erosion depth on the slope gullies and slope in jute fiber slope protection area reduced by 42.08% and 30.71% respectively compared with the control. 2) The interception trough formed by jute fiber slope protection effectively stored water and soil materials, and the soil sedimentation thickness in the interception trough from top to bottom along the slope showed a linear increasing trend. 3) Both sack and sackcloth slope protection effectively inhibited water erosion on the slope surface. Compared with the control, the depth of soil erosion on the gullies and slopes with sack slope protection and sackcloth slope protection reduced by 16.39%, 51.64%, and, 48.30%, 38.10%, respectively. 4) 4, 8 and 10 m sackcloth slope protection effect was different, the erosion depth in the gully reduced by 51.64%, 51.91% and 48.36% respectively compared with the control, the erosion depth on the slope reduced by 38.10%, 43.54% and 16.33% respectively compared with the control. 5) During the 2-3 years monitoring period, there was no significant change in soil erosion depths inside the gullies and slope surfaces with 4 and 8 m specification of the sackcloth. There was remarkable soil erosion on the protected areas with 10 m specification of the sackcloth, and the average erosion depth in the gullies and slope surfaces increased by 53.13% and 34.03% until 3rd year compared to the control. [Conclusions] Based on the difficulty of construction and the cost of materials, it is recommended to use 4-8 m specification with sackcloth to protect the side slope of the dump in the practice of water erosion protection. This study provides a theoretical basis for the slope water and soil erosion protection technology in the mining area.
Effects of plant allocation patterns on soil nutrients and their stoichiometry in red soil slope
[Background] Intensive human activities and specific natural conditions cause soil and water losses in Shenzhen frequently occur. Plantation is the main measure to prevent soil erosion and restore ecological environment. Soil nutrient stoichiometry contains abundant information such as the interaction between vegetation and soil, and soil nutrient limitation on vegetation growth. Studying the soil nutrients and their stoichiometric characteristics after plantation is conducive to understanding the effect of vegetation improvement on soil quality, which is instructive to the soil erosion control and ecological restoration in this area. [Methods] In order to explore the effects of plant allocation patterns on soil nutrients and their stoichiometry in red soil slope after a long time of vegetation reconstruction, this paper selected plots in Shenzhen Soil and Water Conservation Demonstration Garden as an example, on which vegetation reconstruction has been implemented for 10 years. Soils in depths of 0-10, 10-20 and 40-50 cm were taken from the plots of three different plant allocation patterns (grass land, wood land, wood & shrub land), as well as bare land for comparison, and the soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), alkaline nitrogen (AN), available phosphorus (AP), and their stoichiometry were determined.[Results] 1) The main contributing layer of plants on soil nutrients was 0-10 cm surface layer. The improvement of surface soil SOC, TN and AN was the most significant in wood & shrub land, while the improvement of surface soil TP and AP was the most significant in wood land. 2) Surface soil C∶N significantly increased after vegetation reconstruction, but had no significant difference between the three plant allocation patterns (P>0.05). The surface soil C∶P and N∶P of wood & shrub land were both significantly higher than those of grass land and wood land (P<0.05). 3) The stoichiometric ratios of C, N, P were controlled by the amount of soil C and N. The coupling relationship between C and N was stable. Soil C∶P and N∶P had extremely significant positive correlations with C and N (P<0.01). [Conclusions] Soil nutrients and their stoichiometric characteristics are both influenced by soil depth and plant allocation patterns. Vegetation reconstruction demonstrate obvious effects on the improvement of soil quality. The improvement of soil C, N by wood & shrub with high C∶P and N∶P meanwhile is more significant than the independent performance of woods and grasses. N is the main limiting element of vegetation growth in the study area as it is more easily lost by soil erosion. The results of this study can provide references for the optimal allocation and performance evaluation of vegetation reconstruction in the soil erosion area of Shenzhen.
Effects of Pinus massoniana in soil erosion area in South China on rainfall redistribution
[Background] Changting county in Fujian province is one of the most severely eroded granite red soil counties in southern China. Rainfall kinetic energy is the direct driving force of soil erosion in the southern red soil area, and it is also the main cause of soil erosion. Studying the rainfall redistribution characteristics of Pinus massoniana in Changting county of Fujian province will provide a theoretical basis for soil erosion control. [Methods] Taking 36 P. massoniana in Hetian town, a typical southern soil erosion area, as the research object, we continuously observed the rainfall, throughfall, and stem flow outside the forest from May to November 2018. The relationship between throughfall, stem flow, canopy interception and rainfall, rainfall intensity were studied, and the correlation analysis and fitting of rainfall data with DBH (diameter at breast height), tree height, crown width, and LAI (leaf area index) were carried out to study the impact on rainfall redistribution. A total of 90 rainfall events were observed. [Results] 1) The cumulative rainfall outside the forest was 1 191.0 mm, the throughfall was 1 018.7 mm, the canopy interception was 156.9 mm, and the stem flow was 15.4 mm. 2) The throughfall, canopy interception, and stem flow accounted for the cumulative total 85.53%, 13.17% and 1.29% of rainfall. 3) Rainfall and rainfall intensity were significantly correlated with rainfall redistribution and had a good fitting effect. From the calculation of the fitting equation, it can be seen that throughfall was generated when the rainfall exceeded 1.53 mm, and the stem flow was generated when the rainfall exceeded 2.82 mm.4) LAI had a logarithmic function relationship with penetrating rain and canopy interception, and canopy width had an exponential function relationship with stem flow. [Conclusions] By observing the rainfall of the P. massoniana forest in the typical soil erosion area in the South China, the redistribution characteristics of the P. massoniana rainfall are obtained, and scientific guidance is provided for the management of the P. massoniana forest in the soil erosion area.
ZHANG Jing, JIA Hongwen, LI Yuanhang, ZUO Yafan, LIN Sha, WANG Shuaijun, WANG Zuoxiao, HE Kangning
Evaluation of litter and soil water-holding capacity of typical stand in Datong, Qinghai
[Background] Since the implementation of the Grain for Green Program in Datong county of Qinghai province, the existing forest area has been growing steadily, but due to the single forest structure, poor stability and lack of tending and management, the ecological service functions such as water conservation and soil and water conservation in this region are weak. It is of great significance for rational management of plantation and improvement of water conservation function of forest ecosystem to understand and evaluate the water-holding capacity of each forest stand. [Methods] Six typical forest stand types of Populus cathayana, Betula platyphylla, Picea crassifolia, Larix principis-rupprechtii, Picea crassifolia & Betula platyphylla, Picea crassifolia & Larix principis-rupprechtii in Ta'ergou watershed of Datong county,Qinghai province were taken as the research objects. PCA (principal component analysis) was used to select the main influencing factors and construct the evaluation index system, and then fuzzy matter element method was applied to give objective weight. Finally, the water-holding capacity of 6 typical forest stand types in Ta'ergou watershed of Datong county was evaluated by comprehensive scoring method. [Results] 1) The thickness and volume of litters in coniferous forests were the largest. The maximum water-holding capacity of litter ranged from 58.91-107.84 t/hm2, and that of the P. crassifolia & L. principis-rupprechtii was the largest. The effective water-holding capacity of litter ranged from 31.74-60.14 t/hm2. The P. crassifolia & B. platyphylla was the largest, and the maximum value was 1.89 times as much as the minimum value. 2) Soil physical properties were generally mixed conifer-broadleaf forest > broad-leaved forest > coniferous forest. The variation range of field water-holding capacity in 0-20 cm soil layer was 40.58-63.15 t/hm2, and the P. crassifolia & B. platyphylla was the largest, which had significant difference with other stands (P<0.05). 3) The weight value of soil layer accounted for 66%, which was higher than that of litter layer (34%). Soil layer was the main influence layer on water-holding capacity of forest land. 4) The water-holding capacity of each forest type was as follows: P. crassifolia & B. platyphylla > B. platyphylla > P. crassifolia > P. crassifolia & L. principis-rupprechtii > L. principis-rupprechtii > P. cathayana. [Conclusions] The P. crassifolia & B. platyphylla was the best stand of water conservation capacity in Datong county, Qinghai province. This study screened out the best stand type and obtained the mechanism of the difference of stand water holding function, which provided a theoretical basis for the near-natural management of plantations in the eastern part of Qilian Mountains.
HU Yang, ZHANG Junjiao, SHI Changqing, ZHAO Tingning, LIU Xiaoyong, WU Chuan, LIU Bingru
Effects of water-retaining agent content on the water-holding characteristics of soil in waste dump
[Background] The waste dump soil(muck)produced by the open-pit coal mines is an artificial loose accumulation with poor water-holding characteristics and uneven pore distribution, which is not conducive to vegetation growth. This phenomenon is more serious in arid and semi-arid areas and has become an important factor restricting the use of vegetation for ecological restoration in mining areas. Based on this, different water-retaining agent content were applied to the muck of Ningxia open-pit coal mine to improve the water-holding characteristics, water availability and pore environment of the muck, and the optimal content was selected. [Methods] We set up 3 sampling points on the upslope, mid-slope, and downslope at the dumping site of Dafeng Mine in Rujigou, Shizuishan city, Ningxia. We then collected and mixed 0-20 cm muck, then passed them through a 2 mm soil sieve and determined its density and particle composition. The soil high-speed centrifuge was used to simulate the dehumidification process of the muck containing water-retaining agent, and Van Genuchten model was used to analyze the effect of the soil water characteristic curve, fitting parameters, water availability and pore distribution of the muck with different water-retaining agent content. [Results] 1) Muck’s water content decreased sharply with the increase of soil water suction at low suction stage, and it was positively correlated with water-retaining agent content, but the downward trend slowed down at low suction stage and had no significant change at high suction stage. 2) Saturated water content(θs)increased with the increase of water-retaining agent content. The inverse of air-entry value (α) reduced siginificantly by the use of water-retaining agent, but it increased first and then decreased, and the peak appeared at 1.0% treatment. Residual water content(θr)had no significant difference, and the value of shape parameter(n) had no obvious change rule.3) Water-retaining agent increased the total available water and easily available water content of muck by 1.12-3.31 times and 1.11-3.29 times respectively. The high water-retaining agent content(1.0%,1.5% and 2.0%)significantly increased slowly available water content by 3.00-4.38 times, and the unavailable water content only significantly reduced in 0.2% and 0.5% treatment. 4) The water-retaining agent significantly increased the mesopore by 1.2-2.6 times, the micropore by 1.8-3.8 times, and the super micropore by 1.2-4.7 times. [Conclusions] Our results reveal that water-retaining agent relies on its capillary pore to improve the water-holding characteristics of muck. The increase in its content may significantly increase the total available water content, easily available water content, and the ratio of mesopore,micropore,and super micropore. In order to be suitable for vegetation growth, water-retaining agent content applied to the muck should be <1.0%, and 0.5% is the optimal one.
ZOU Hang, SONG Yali, WANG Keqin, ZHANG Zhuanmin, XING Jinmei
Effects of mining on the carbon loss of natural forest ecosystem in mining area
[Background] In the rapid development of the social economy, the demand for mineral resources is increasing. Due to large-scale and unreasonable mining activities, the mining environment was seriously damaged, resulting in a large number of abandoned land, which could not be restored in a short period. The continuous degradation of forest ecological environment, soil erosion and soil degradation lead to the significant reduction of vegetation and soil carbon storage. Therefore, artificial measures are urgently needed to restore the ecosystem affected by mining.[Methods]This paper chose the mining area of Zhuang and Miao autonomous prefecture in Wenshan of Yunnan province (the vegetation was completely destroyed) as the research object. The carbon storage of forest ecosystem under natural conditions was analyzed to measure the loss of forest carbon in mining area. Organic carbon content and storage characteristics of arbor layers (leaves, branches, trunk, bark and roots), shrub layers (leaves, roots and branches), herb layers (aboveground and underground parts), litter layers (fresh litter layer, fragmented litter layer and humified litter layer) and soil layers (0-10, 10-20, 20-30, 30-40 and 40-60 cm) were studied. [Results] 1) In the vegetation layer of the mining area ecosystem, the carbon loss of the arbor layer was the main body of the vegetation layer loss (94.6%), followed by the shrub layer (3.4%), litter layer (1.1%) and herb layer (0.9%) were relatively small; 2) After mining, it also caused serious soil carbon loss. The soil organic carbon content and carbon loss in the forest ecosystem of the mining area decreased gradually with the increase of the soil layer. The soil carbon loss was mainly concentrated in the topsoil layer of 0-30 cm, accounting for 64.2% of the total soil carbon loss. 3) After mining, the total vegetation carbon loss reached 288.4 t/hm2, and the total soil carbon loss reached 169.9 t/hm2. Artificial mining destroyed the natural vegetation of the forest, resulting in a high amount of carbon loss in the soil layer and vegetation layer of the mining area. [Conclusions] Under the natural condition in the study area, forest ecosystems has a strong ability of carbon storage, high carbon loss happened after mining for many years. Vegetation restoration technology should be adopted to restore the ecological integrity and land productivity of the damaged land in the mining area, so as to improve the soil quality of the mining area and increase the carbon storage of the forest ecosystem.
Effect of petroleum pollution on the composition and diversity of bacterial community in Phragmites australis rhizosphere
[Background] Petroleum pollution caused by accidents in petroleum production and transportation will change soil physical and chemical properties, resulting in soil erosion and serious damage to the ecological environment. Phragmites australis is a plant with strong stress resistance, which often is used as a plant material for ecological restoration. It plays an important role in resistance to stress through interaction with rhizosphere bacterial community. Petroleum pollution has a significant influence on the structure and diversity of rhizosphere bacterial community, which may be one of the important factors hindering the growth and development of P. australis in petroleum contaminated soil. [Methods] In order to reveal the effects of different concentrations of petroleum pollution on soil and rhizosphere bacterial community of P. australis, soil samples and P. australis rhizomes were collected from Zhalong wetland. P. australis rhizomes planted in soil which had used to simulate mild (3 g/kg), moderate (6 g/kg), and severe (12 g/kg) petroleum pollution. Cultured for 60 d, then soil ammonium nitrogen, available phosphorus, available potassium, and organic matter were measured. The community abundance and composition of the P. australis rhizosphere bacteria under different soil petroleum treatments were detected by high-throughput sequencing and bioinformatics method. [Results] Petroleum pollution significantly increased the content of ammonium nitrogen, available phosphorus and organic matter in soil, respectively by 41%, 121% and 141%, but had no significant effect on soil pH value and available potassium. The high-throughput sequencing showed that P. australis rhizosphere soil contained 33 phyla and 111 genera of bacteria, of which Proteobacteria was the dominant bacterium with a proportion from 37.31%-46.6%. There were 23 genera of dominant bacteria (relative abundance >1%), of which Pseudomonas and Hydrogenophaga was the dominant genus that demonstrated good adaptability to petroleum pollution. The bacteria diversity was the lowest in the slight polluted soil, and the highest in the severe polluted soil. Petroleum pollution promoted the growth of Pseudomonas and Hydrogenophaga, and inhibited the growth of Exiguobacterium, Rhodoligotrophos, Citrobacter, Aridibacter, Azoarcus, Gp21, and Mongoliicoccus. Slight petroleum pollution promoted the growth of Desulfuromonas and Bellilinea, and high petroleum pollution inhibits its growth. [Conculsions] Petroleum pollution changed soil nutrient content and had a significant effect on bacterial community structure and diversity in the rhizosphere soil of P. australis.
ZHOU Ruipeng, QU Liqin, ZHAO Ying, DU Pengfei, CHEN Yin, NING Duihu
Soil erosion survey system in the United States and its evolution characteristics
[Background] Soil erosion causes a serious threat to the soil and water resources on which human beings depend at the global scale, and soil erosion survey and assessment at the global/regional and national scale is an important basis for solving this global resource and environmental issue. [Methods] This study introduced the background and basic structure of the Conservation Needs Inventory (CNI), and focuses on the system design, model involved for soil erosion estimation, sampling methods, data composition and publication system of the National Resources Inventory (NRI). The system design, modeling method, sampling design, data composition and publication system of the National Resources Inventory (NRI) were analyzed. In addition, the composition characteristics of the major land use types involved in the U.S. soil erosion survey in the past 35 years were analyzed. Based on the relatively complete land use statistics and soil erosion survey results of the NRI, the soil erosion status and evolution characteristics of different land use types in the different regions were studied. [Results] The development of soil erosion survey in the U.S. are in three distinct periods: the initial stage (Pre-NRI), the CNI stage and the NRI stage. The NRI system, which has been used since 1977, is a comprehensive survey of natural resources developed from soil erosion survey based on sampling and statistical analysis. The soil erosion survey in NRI involved three land use types of Cropland, Pastureland, and Conservation Reserve Program (CRP). According to the newest NRI summary report released in 2020, the total area of cropland decreased by 2.7% from 1982 to 2017, Pastureland did not change much, and the overall trend of CRP land increased first and then decreased after its implementation since 1986. From 1982 to 2017, at the national scale, both water and wind erosion in the United States showed a decreasing trend with 39.9% and 44.71% reduction, respectively, with a small increasing trend in water erosion from 2007 to 2017. At the regional scale, both water and wind erosion decreased significantly to stable levels in all six regions, with different degrees of reduction in each region, but the overall pattern remained largely unchanged. For the three land use types involved in erosion, there was a significant and sustained increase in wind erosion rates since 2002 for pastureland and CRP land, based on an overall significant decrease on a 35-year scale. [Conclusions] This study may provide reference, insights or lessons for the establishment of soil erosion investigation system at regional and national scales. In addition, the erosion evolution pattern in the United States in the past 35-year may provide a scientific basis for studying the erosion evolution pattern and formulating sustainable soil and water conservation development plans.
